Jamieson, Fausset and Brown on Exodus 21:23-25

23-25. eye for eye--The law which authorized retaliation (a principle acted upon by all primitive people) was a civil one. It was given to regulate the procedure of the public magistrate in determining the amount of compensation in every case of injury, but did not encourage feelings of private revenge. The later Jews, however, mistook it for a moral precept, and were corrected by our Lord (Mt 5:38-42).